<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div>ul>li>a{
            background-color: red;
        }
        #bg{
            background-color: blueviolet;
         }
        .licolor{
            background-color: yellow;
        }
        h3,p{
            color: yellowgreen;
        }
    </style>
</head>
<body>

   <div>
       <ul>
           <li><a href="index.html">AAA</a></li>
           <li><a href="index.html">AAA</a></li>
           <li><a href="index.html">AAA</a></li>
       </ul>
   </div>
   <div>
       <ol>
           <li><a href="index.html" id="bg">BBB</a></li>
           <li><a href="index.html" class="licolor">BBB</a></li>
           <li><a href="index.html" class="licolor">BBB</a></li>
       </ol>
   </div>
   <div>
       <h3>这是一个标题</h3>
       <p>第一个段落</p>
   </div>

</body>
</html>